1. Technical Field
The invention is related to media cutting mechanisms for roll fed pen plotters.
2. Background Art
Pen plotters which plot on a media fed from a roll are known in the art. As depicted in FIG. 1, in such a plotter there is a plotting bed 10 over which the media 12 from the roll 14 is moved to create movement in one axis of the coordinate system of the plotter. A pen 16 is carried by a pen carriage 18 which moves laterally along a support beam 20 to create movement in the other axis of the coordinate system. At some point in the process, the portion of the media 12 containing the plot must be separated from the rest of the media 12 connected to the roll 14. This is typically accomplished by a cutting mechanism of the plotter in much the same way as roll-fed facsimile machines cut off individual pages, for example. Such a cutting mechanism 22 is depicted in simplified form in FIG. 2. The mechanism 22 comprises a moving carriage 24 carrying a cutting wheel 26. To cut the media 12, the carriage 24 is moved across the plotting bed 10 from one side to the other as indicated by the arrow 28. The cutting wheel 26 rolls across the media 12 and the sharp edge thereof cuts the media 12.
In devices such as facsimile machines which don't have a laterally moving member such as the pen carriage 18, the moving carriage 24 of the cutting mechanism 22 must be separate and separately powered. In a pen plotter, however, it is possible to mount the cutting wheel 26 to the pen carriage 18 as depicted in FIG. 3 and to employ the pen carriage 18 as the moving carriage 24 of the cutting mechanism 22. This approach, on the other hand, adds problems and considerations of its own. Since the pen carriage 18 is constantly in motion during the plotting process, some provision must be made to move the cutting wheel 26 out of the way during plotting and into a cutting position for cutting. The pen 16 is already carried by a lifting and lowering mechanism so that is not a problem or consideration. To accomplish this, a typical prior art approach would be to have the cutting wheel 26 mounted on a linkage 30 operated by an electrical solenoid 32. This, of course, adds substantially to the complexity of the construction of the pen carriage 18 which in turn adds to the cost of manufacture. It also adds substantial weight and mass to the pen carriage 18 which requires stronger components and can deteriorate the performance of the plotter due to the added time to overcome inertia of the greater mass when reversing direction of the pen carriage.
Wherefore, it is an object of the present invention to provide a cutting mechanism for roll-fed pen plotters which is carried by the pen carriage but which does not require an electrical solenoid for its operation.
It is another object of the present invention to provide a cutting mechanism for roll-fed pen plotters which is carried by the pen carriage and which is of low mass.
It is still another object of the present invention to provide a cutting mechanism for roll-fed pen plotters which is carried by the pen carriage and which is mechanically actuated.
Other objects and benefits of the invention will become apparent from the detailed description which follows hereinafter when taken in conjunction with the drawing figures which accompany it.